A Simple Crystallography Question

[ian_K_Robinson]

Hi

could anyone help with a simple crystallography question.

I am studying domain growth in crystals via Monte-Carlo simulations of atomistic models. I am writing a program to simulate the (neutron ) scattering pattern from a data-file of atomic positions via the rather brute force method of summing the scattered wave intensities at each point on a detector.

If I want to generate a pattern from a particular orientation – say 4,2,0 planes. Should the incident beam be perpendicular to the desired plane with the detector at some distance perpendicular to the incident ray or should the beam be at some arbitrary angle such as 1,1,0 with the detector oriented at 4,2,0 ?

Any suggestions very gratefully received

Ian Robinson

an ancient Ph.D candidate

 

[M Quack]

The incident and diffracted beam should form the Bragg angle with the 4,2,0 planes. There is a remaining degree of freedom, rotation within the planes, that is referred to as "azimuth". For your calculations that should not matter.

This is a very common technique used in x-ray diffraction known as diffraction topography or diffraction tomography.

If you want to see how the domain distribution affects the peak shape, then you also have to calculate the diffracted intensity for angles slightly smaller or larger than the nominal Bragg angle.